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[GHC] #15695: Core Lint error, from -fobject-code + defer type errors + pattern synonyms + other stuff
by GHC 14 Oct '18

14 Oct '18

#15695: Core Lint error, from -fobject-code + defer type errors + pattern synonyms + other stuff -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.6.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Compile-time Unknown/Multiple | crash or panic Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Try running this (`-fobject-code` is required) with '''and''' without `-dcore-lint`. I tried to minimize it but it is still hefty. This is showing it without `-dcore-lint`: {{{#!hs {-# Language RankNTypes, PatternSynonyms, DataKinds, PolyKinds, GADTs, TypeOperators, MultiParamTypeClasses, TypeFamilies, TypeSynonymInstances, FlexibleInstances, InstanceSigs, FlexibleContexts #-} {-# Options_GHC -fdefer-type-errors #-} import Data.Kind import Data.Type.Equality data TyVar :: Type -> Type -> Type where VO :: TyVar (a -> as) a VS :: TyVar as a -> TyVar (b -> as) a data NP :: (k -> Type) -> ([k] -> Type) where Nil :: NP f '[] (:*) :: f a -> NP f as -> NP f (a:as) data NS :: (k -> Type) -> ([k] -> Type) where Here :: f a -> NS f (a:as) There :: NS f as -> NS f (a:as) infixr 6 :&: data Ctx :: Type -> Type where E :: Ctx(Type) (:&:) :: a -> Ctx(as) -> Ctx(a -> as) data NA a type SOP(kind::Type) code = NS (NP NA) code data ApplyT(kind::Type) :: kind -> Ctx(kind) -> Type where AO :: a -> ApplyT(Type) a E AS :: ApplyT(ks) (f a) ctx -> ApplyT(k -> ks) f (a:&:ctx) from' :: ApplyT(Type -> Type -> Type) Either ctx -> NS (NP NA) '[ '[VO] ] from' (ASSO (Left a)) = Here (a :* Nil) from' (ASSO (Right b)) = There (Here undefined) pattern ASSO :: () => forall (ks :: Type) k (f :: k -> ks) (a1 :: k) (ks1 :: Type) k1 (f1 :: k1 -> ks1) (a2 :: k1) a3. (kind ~ (k -> k1 -> Type), a ~~ f, b ~~ (a1 :&: a2 :&: E), f a1 ~~ f1, f1 a2 ~~ a3) => a3 -> ApplyT kind a b pattern ASSO a = AS (AS (AO a)) }}} {{{ $ latestbug -fobject-code 466.hs GHCi, version 8.7.20180828: http://www.haskell.org/ghc/ :? for help [1 of 1] Compiling Main ( 466.hs, 466.o ) 466.hs:35:14: warning: [-Wdeferred-type-errors] • Could not deduce: a2 ~ NA 'VO from the context: ((* -> * -> *) ~ (k1 -> k2 -> *), Either ~~ f, ctx ~~ (a2 ':&: (a3 ':&: 'E)), f a2 ~~ f1, f1 a3 ~~ a4) bound by a pattern with pattern synonym: ASSO :: forall kind (a :: kind) (b :: Ctx kind). () => forall ks k (f :: k -> ks) (a1 :: k) ks1 k1 (f1 :: k1 -> ks1) (a2 :: k1) a3. (kind ~ (k -> k1 -> *), a ~~ f, b ~~ (a1 ':&: (a2 ':&: 'E)), f a1 ~~ f1, f1 a2 ~~ a3) => a3 -> ApplyT kind a b, in an equation for ‘from'’ at 466.hs:35:8-21 ‘a2’ is a rigid type variable bound by a pattern with pattern synonym: ASSO :: forall kind (a :: kind) (b :: Ctx kind). () => forall ks k (f :: k -> ks) (a1 :: k) ks1 k1 (f1 :: k1 -> ks1) (a2 :: k1) a3. (kind ~ (k -> k1 -> *), a ~~ f, b ~~ (a1 ':&: (a2 ':&: 'E)), f a1 ~~ f1, f1 a2 ~~ a3) => a3 -> ApplyT kind a b, in an equation for ‘from'’ at 466.hs:35:8-21 Expected type: a4 Actual type: Either (NA 'VO) a3 • In the pattern: Left a In the pattern: ASSO (Left a) In an equation for ‘from'’: from' (ASSO (Left a)) = Here (a :* Nil) • Relevant bindings include from' :: ApplyT (* -> * -> *) Either ctx -> NS (NP NA) '[ '[ 'VO]] (bound at 466.hs:35:1) | 35 | from' (ASSO (Left a)) = Here (a :* Nil) | ^^^^^^^ 466.hs:36:26: warning: [-Wdeferred-type-errors] • Couldn't match type ‘a0 : as0’ with ‘'[]’ Expected type: NS (NP NA) '[ '[ 'VO]] Actual type: NS (NP NA) ('[ 'VO] : a0 : as0) • In the expression: There (Here undefined) In an equation for ‘from'’: from' (ASSO (Right b)) = There (Here undefined) • Relevant bindings include from' :: ApplyT (* -> * -> *) Either ctx -> NS (NP NA) '[ '[ 'VO]] (bound at 466.hs:35:1) | 36 | from' (ASSO (Right b)) = There (Here undefined) | ^^^^^^^^^^^^^^^^^^^^^^ WARNING: file compiler/types/TyCoRep.hs, line 2378 in_scope InScope {wild_00 wild_Xl wild_Xv wild_X1m a_a1Gv ks_a1Ou k_a1Ov f_a1Ow a_a1Ox ctx_a1Oy co_a1Oz co_a1OA co_a1OB ks_a1OC k_a1OD f_a1OE a_a1OF ctx_a1OG co_a1OH co_a1OI co_a1OJ a_a1OK co_a1OL co_a1OM co_a1ON as_a1Q3 a_a1Q4 ctx_a1Q5 $krep_a2XW $krep_a2XX $krep_a2XY $krep_a2XZ $krep_a2Y0 $krep_a2Y1 $krep_a2Y2 $krep_a2Y3 $krep_a2Y4 $krep_a2Y5 $krep_a2Y6 $krep_a2Y7 $krep_a2Y8 $krep_a2Y9 $krep_a2Ya $krep_a2Yb $krep_a2Yc $krep_a2Yd $krep_a2Ye $krep_a2Yf $krep_a2Yg $krep_a2Yh $krep_a2Yi $krep_a2Yj $krep_a2Yk $krep_a2Yl $krep_a2Ym $krep_a2Yn $krep_a2Yo $krep_a2Yp $krep_a2Yq $krep_a2Yr $krep_a2Ys $krep_a2Yt $krep_a2Yu $krep_a2Yv $krep_a2Yw $krep_a2Yx $krep_a2Yy $krep_a2Yz $krep_a2YA $krep_a2YB $krep_a2YC $krep_a2YD $krep_a2YE $krep_a2YF $krep_a2YG $krep_a2YH $krep_a2YI $krep_a2YJ $krep_a2YK $krep_a2YL ds_d2YO ds_d2YP ds_d2YV fail_d2Z2 from' $bASSO $mASSO $tc':&: $tc':* $tc'AO $tc'AS $tc'E $tc'Here $tc'Nil $tc'There $tc'VO $tc'VS $tcApplyT $tcCtx $tcNA $tcNP $tcNS $tcTyVar $trModule $trModule_s2ZM $trModule_s2ZN $trModule_s2ZO $trModule_s2ZP $krep_s2ZQ $krep_s2ZR $krep_s2ZS $krep_s2ZT $krep_s2ZU $krep_s2ZV $krep_s2ZW $krep_s2ZX $tcTyVar_s2ZY $tcTyVar_s2ZZ $krep_s300 $krep_s301 $krep_s302 $krep_s303 $tc'VO_s304 $tc'VO_s305 $krep_s306 $krep_s307 $tc'VS_s308 $tc'VS_s309 $tcNP_s30a $tcNP_s30b $krep_s30c $krep_s30d $krep_s30e $krep_s30f $krep_s30g $krep_s30h $tc':*_s30i $tc':*_s30j $krep_s30k $krep_s30l $krep_s30m $tc'Nil_s30n $tc'Nil_s30o $tcNS_s30p $tcNS_s30q $krep_s30r $krep_s30s $krep_s30t $krep_s30u $krep_s30v $krep_s30w $tc'Here_s30x $tc'Here_s30y $krep_s30z $krep_s30A $krep_s30B $tc'There_s30C $tc'There_s30D $tcCtx_s30E $tcCtx_s30F $krep_s30G $krep_s30H $krep_s30I $tc':&:_s30J $tc':&:_s30K $krep_s30L $krep_s30M $krep_s30N $krep_s30O $krep_s30P $tc'E_s30Q $tc'E_s30R $tcNA_s30S $tcNA_s30T $tcApplyT_s30U $tcApplyT_s30V $krep_s30W $krep_s30X $krep_s30Y $krep_s30Z $krep_s310 $krep_s311 $tc'AS_s312 $tc'AS_s313 $krep_s314 $krep_s315 $krep_s316 $tc'AO_s317 $tc'AO_s318} tenv [a1Ow :-> f_a1Ow, a1Ox :-> a_a1Ox, a1Oy :-> ctx_a1Oy, a1OE :-> f_a1OE, a1OF :-> a_a1OF, a1OG :-> ctx_a1OG] cenv [a1Oz :-> co_a1Oz, a1OA :-> co_a1OA, a1OB :-> co_a1OB, a1OH :-> co_a1OH, a1OI :-> co_a1OI, a1OJ :-> co_a1OJ, a1OL :-> co_a1OL, a1OM :-> co_a1OM, a1ON :-> co_a1ON] tys [a_a1Ox ~# (NA 'VO |> Sym (Nth:2 (Sym co_a2U0)))] cos [] needInScope [a1Ov :-> k_a1Ov, a1OD :-> k_a1OD, a1Q3 :-> as_a1Q3, a1Q4 :-> a_a1Q4, a2U0 :-> co_a2U0] WARNING: file compiler/types/TyCoRep.hs, line 2378 in_scope InScope {wild_00 wild_Xl wild_Xv wild_X1m a_a1Gv ks_a1Ou k_a1Ov f_a1Ow a_a1Ox ctx_a1Oy co_a1Oz co_a1OA co_a1OB ks_a1OC k_a1OD f_a1OE a_a1OF ctx_a1OG co_a1OH co_a1OI co_a1OJ a_a1OK co_a1OL co_a1OM co_a1ON as_a1Q3 a_a1Q4 ctx_a1Q5 $krep_a2XW $krep_a2XX $krep_a2XY $krep_a2XZ $krep_a2Y0 $krep_a2Y1 $krep_a2Y2 $krep_a2Y3 $krep_a2Y4 $krep_a2Y5 $krep_a2Y6 $krep_a2Y7 $krep_a2Y8 $krep_a2Y9 $krep_a2Ya $krep_a2Yb $krep_a2Yc $krep_a2Yd $krep_a2Ye $krep_a2Yf $krep_a2Yg $krep_a2Yh $krep_a2Yi $krep_a2Yj $krep_a2Yk $krep_a2Yl $krep_a2Ym $krep_a2Yn $krep_a2Yo $krep_a2Yp $krep_a2Yq $krep_a2Yr $krep_a2Ys $krep_a2Yt $krep_a2Yu $krep_a2Yv $krep_a2Yw $krep_a2Yx $krep_a2Yy $krep_a2Yz $krep_a2YA $krep_a2YB $krep_a2YC $krep_a2YD $krep_a2YE $krep_a2YF $krep_a2YG $krep_a2YH $krep_a2YI $krep_a2YJ $krep_a2YK $krep_a2YL ds_d2YO ds_d2YP ds_d2YV fail_d2Z2 from' $bASSO $mASSO $tc':&: $tc':* $tc'AO $tc'AS $tc'E $tc'Here $tc'Nil $tc'There $tc'VO $tc'VS $tcApplyT $tcCtx $tcNA $tcNP $tcNS $tcTyVar $trModule $trModule_s2ZM $trModule_s2ZN $trModule_s2ZO $trModule_s2ZP $krep_s2ZQ $krep_s2ZR $krep_s2ZS $krep_s2ZT $krep_s2ZU $krep_s2ZV $krep_s2ZW $krep_s2ZX $tcTyVar_s2ZY $tcTyVar_s2ZZ $krep_s300 $krep_s301 $krep_s302 $krep_s303 $tc'VO_s304 $tc'VO_s305 $krep_s306 $krep_s307 $tc'VS_s308 $tc'VS_s309 $tcNP_s30a $tcNP_s30b $krep_s30c $krep_s30d $krep_s30e $krep_s30f $krep_s30g $krep_s30h $tc':*_s30i $tc':*_s30j $krep_s30k $krep_s30l $krep_s30m $tc'Nil_s30n $tc'Nil_s30o $tcNS_s30p $tcNS_s30q $krep_s30r $krep_s30s $krep_s30t $krep_s30u $krep_s30v $krep_s30w $tc'Here_s30x $tc'Here_s30y $krep_s30z $krep_s30A $krep_s30B $tc'There_s30C $tc'There_s30D $tcCtx_s30E $tcCtx_s30F $krep_s30G $krep_s30H $krep_s30I $tc':&:_s30J $tc':&:_s30K $krep_s30L $krep_s30M $krep_s30N $krep_s30O $krep_s30P $tc'E_s30Q $tc'E_s30R $tcNA_s30S $tcNA_s30T $tcApplyT_s30U $tcApplyT_s30V $krep_s30W $krep_s30X $krep_s30Y $krep_s30Z $krep_s310 $krep_s311 $tc'AS_s312 $tc'AS_s313 $krep_s314 $krep_s315 $krep_s316 $tc'AO_s317 $tc'AO_s318} tenv [a1Ow :-> f_a1Ow, a1Ox :-> a_a1Ox, a1Oy :-> ctx_a1Oy, a1OE :-> f_a1OE, a1OF :-> a_a1OF, a1OG :-> ctx_a1OG] cenv [a1Oz :-> co_a1Oz, a1OA :-> co_a1OA, a1OB :-> co_a1OB, a1OH :-> co_a1OH, a1OI :-> co_a1OI, a1OJ :-> co_a1OJ, a1OL :-> co_a1OL, a1OM :-> co_a1OM, a1ON :-> co_a1ON] tys [a_a1Ox ~# (NA 'VO |> Sym (Nth:2 (Sym co_a2U0)))] cos [] needInScope [a1Ov :-> k_a1Ov, a1OD :-> k_a1OD, a1Q3 :-> as_a1Q3, a1Q4 :-> a_a1Q4, a2U0 :-> co_a2U0] Ok, one module loaded. Prelude Main> }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15695> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15481: TH fails to recover from reifyFixity with -fexternal-interpreter
by GHC 14 Oct '18

14 Oct '18

#15481: TH fails to recover from reifyFixity with -fexternal-interpreter -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.8.1 Component: Template | Version: 8.4.3 Haskell | Keywords: RemoteGHCi | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- (Originally reported at https://github.com/glguy/th- abstraction/issues/53.) If you compile the following program: {{{#!hs {-# LANGUAGE TemplateHaskell #-} module Bug where import Language.Haskell.TH main :: IO () main = putStrLn $(recover (stringE "reifyFixity failed") (do foo <- newName "foo" _ <- reifyFixity foo stringE "reifyFixity successful")) }}} It will work fine without the use of `-fexternal-interpreter`. However, using `-fexternal-interpreter` will result in an error: {{{ $ /opt/ghc/8.4.3/bin/ghc Bug.hs -fforce-recomp [1 of 1] Compiling Bug ( Bug.hs, Bug.o ) $ /opt/ghc/8.4.3/bin/ghc Bug.hs -fforce-recomp -fexternal-interpreter [1 of 1] Compiling Bug ( Bug.hs, Bug.o ) Bug.hs:7:19: error: • The exact Name ‘foo_a3MT’ is not in scope Probable cause: you used a unique Template Haskell name (NameU), perhaps via newName, but did not bind it If that's it, then -ddump-splices might be useful • In the untyped splice: $(recover (stringE "reifyFixity failed") (do foo <- newName "foo" _ <- reifyFixity foo stringE "reifyFixity successful")) | 7 | main = putStrLn $(recover (stringE "reifyFixity failed") | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^... Bug.hs:7:19: error: • The exact Name ‘foo_a3MT’ is not in scope Probable cause: you used a unique Template Haskell name (NameU), perhaps via newName, but did not bind it If that's it, then -ddump-splices might be useful • In the untyped splice: $(recover (stringE "reifyFixity failed") (do foo <- newName "foo" _ <- reifyFixity foo stringE "reifyFixity successful")) | 7 | main = putStrLn $(recover (stringE "reifyFixity failed") | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^... }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15481> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12005: Constraint instances not shown in `:info`
by GHC 13 Oct '18

13 Oct '18

#12005: Constraint instances not shown in `:info` -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.3 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- {{{ $ ghci -ignore-dot-ghci -XKindSignatures -XRank2Types -XConstraintKinds -XAllowAmbiguousTypes -XInstanceSigs GHCi, version 8.1.20160428: http://www.haskell.org/ghc/ :? for help Prelude> import Data.Kind Prelude Data.Kind> class Defer (p :: Constraint) where defer :: (p => r) -> r Prelude Data.Kind> instance Defer () where defer :: r -> r; defer = id Prelude Data.Kind> :i Defer class Defer (p :: Constraint) where defer :: (p => r) -> r {-# MINIMAL defer #-} -- Defined at <interactive>:2:1 }}} Same happens with the [https://github.com/ekmett/constraints/blob/master/src/Data/Constraint/Defer… Data.Constraint.Deferrable] which defines: {{{#!hs instance (Typeable a, Typeable b) => Deferrable (a ~ b) instance (Deferrable a, Deferrable b) => Deferrable (a, b) instance (Deferrable a, Deferrable b, Deferrable c) => Deferrable (a, b, c) }}} but no instances are shown: {{{ ghci> import Data.Constraint.Deferrable ghci> :i Deferrable class Deferrable (p :: Constraint) where deferEither :: proxy p -> (p => r) -> Either String r {-# MINIMAL deferEither #-} -- Defined in ‘Data.Constraint.Deferrable’ }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12005> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15722: Add -Wstar-is-type to the User's Guide
by GHC 13 Oct '18

13 Oct '18

#15722: Add -Wstar-is-type to the User's Guide -------------------------------------+------------------------------------- Reporter: int-index | Owner: (none) Type: task | Status: new Priority: normal | Milestone: 8.6.2 Component: Documentation | Version: 8.6.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): Phab:D5203 | Wiki Page: -------------------------------------+------------------------------------- Documentation for `-Wstar-is-type` is missing in the 8.6.1 release. Creating this ticket with a milestone as a reminder to cherry-pick the patch to 8.6.2 (right now it's merged to `master`). -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15722> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15571: Eager AP_STACK blackholing causes incorrect size info for sanity checks
by GHC 13 Oct '18

13 Oct '18

#15571: Eager AP_STACK blackholing causes incorrect size info for sanity checks -------------------------------------+------------------------------------- Reporter: osa1 | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Runtime | Version: 8.5 System | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: #15508 Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- While debugging #15508 I found a case where eager blackholing in AP_STACK causes `closure_sizeW()` to return incorrect size, which in turn causes incorrect slop zeroing by `OVERWRITING_CLOSURE()`, which breaks sanity checks. To reproduce, cd into `testsuite/tests/concurrent/prog001`, then: {{{ $ ghc-stage2 Mult.hs -fforce-recomp -debug -rtsopts $ ./Mult +RTS -DS Mult: internal error: checkClosure: stack frame (GHC version 8.7.20180825 for x86_64_unknown_linux) Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug zsh: abort (core dumped) ./Mult +RTS -DS }}} Here's how the problem occurs: 1. Allocate an AP_STACK in a generation during a GC. 2. Evaluate the AP_STACK. The entry code first WHITEHOLEs and then eagerly BLACKHOLEs it. At this point size of the STACK becomes 2 because that's the size of (eager or not) BLACKHOLE. 3. To start a GC the thread does `threadPaused`, which in line 342 actually BLACKHOLEs the eager blackhole (is this part really correct?) and zeros the slop, but because the eager blackhole has the same size as BLACKHOLE it doesn't actually zero the stack frames in the original AP_STACK's payload. 4. In the next GC, in pre-GC sanity check we check the whole heap. When checking the generation that the BLACKHOLE (the AP_STACK that became a BLACKHOLE in step (2)) resides in we check the closure, and then check `closure + 2` (2 is the size of BLACKHOLE) instead of `closure + <size of the stack>`, and end up checking a stack frame of the original AP_STACK. This causes the sanity check to fail because we don't expect to see a stack frame outside of a stack. In summary, normally when blackhole an object we zero the space after the blackhole (i.e. some part of the original object's payload) so that in sanity checks we can skip over that space, but we can't do this when eagerly blackholing (because the payload of the original object will be used) which causes sanity check failures. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15571> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15053: Compiler panic on invalid syntax (unterminated pragma)
by GHC 13 Oct '18

13 Oct '18

#15053: Compiler panic on invalid syntax (unterminated pragma) -------------------------------------+------------------------------------- Reporter: AndreasK | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.2.2 (Parser) | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Compile-time Unknown/Multiple | crash or panic Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- The following minimal example causes a compiler panic. {{{ {-# OPTIONS_GHC -O1 } " #-} }}} {{{ ghc-stage2.exe: panic! (the 'impossible' happened) (GHC version 8.5.20180413 for x86_64-unknown-mingw32): getOptions'.parseToks: Couldn't read "\r\n\"\r\n " as String Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} Happens in HEAD and 8.2.2 at least. Double quotes seem to confuse the parser. Also panics if there are two doublequotes. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15053> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14907: Error message: (%, %) shows up when with accidental paren
by GHC 13 Oct '18

13 Oct '18

#14907: Error message: (%,%) shows up when with accidental paren -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.5 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Poor/confusing Unknown/Multiple | error message Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- I accidentally wrote an extra closing parens in instance declaration {{{#!hs $ ghci -ignore-dot-ghci -XRankNTypes GHCi, version 8.2.1: http://www.haskell.org/ghc/ :? for help Prelude> class (Category (Src f), forall xx. xx => Eq xx)) => Functor f <interactive>:1:8: error: Unexpected type ‘Category (Src f)’ In the class declaration for ‘GHC.Classes.(%,%)’ A class declaration should have form class GHC.Classes.(%,%) a b where ... Prelude> }}} `(%,%)` shouldn't show up here, same happens on 8.5.20180105 -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14907> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8763: forM_ [1..N] does not get fused (10 times slower than go function)
by GHC 13 Oct '18

13 Oct '18

#8763: forM_ [1..N] does not get fused (10 times slower than go function) ------------------------------+-------------------------------------------- Reporter: nh2 | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.6.3 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Runtime performance bug Unknown/Multiple | Test Case: Difficulty: Unknown | Blocking: Blocked By: | Related Tickets: | ------------------------------+-------------------------------------------- Apparently idiomatic code like {{{forM_ [1.._N]}}} does not get fused away. This can give serious performance problems when unnoticed. {{{ -- Slow: forM_ [0.._N-1] $ \i -> do ... -- Around 10 times faster: loop _N $ \i -> do ... {-# INLINE loop #-} loop :: (Monad m) => Int -> (Int -> m ()) -> m () loop bex f = go 0 where go !n | n == bex = return () | otherwise = f n >> go (n+1) }}} Full code example: https://gist.github.com/nh2/8905997 - the relevant alternatives are commented. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8763> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15196: Invert floating point comparisons such that no extra parity check is required.
by GHC 13 Oct '18

13 Oct '18

#15196: Invert floating point comparisons such that no extra parity check is required. -------------------------------------+------------------------------------- Reporter: AndreasK | Owner: (none) Type: task | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.4.3 (NCG) | Keywords: CodeGen | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- This comment pretty much explains it already: {{{ -- We have to worry about unordered operands (eg. comparisons -- against NaN). If the operands are unordered, the comparison -- sets the parity flag, carry flag and zero flag. -- All comparisons are supposed to return false for unordered -- operands except for !=, which returns true. -- -- Optimisation: we don't have to test the parity flag if we -- know the test has already excluded the unordered case: eg > -- and >= test for a zero carry flag, which can only occur for -- ordered operands. -- -- ToDo: by reversing comparisons we could avoid testing the -- parity flag in more cases. }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15196> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15499: Panic in occurence analysis phase (?), getRuntimeRep
by GHC 13 Oct '18

13 Oct '18

#15499: Panic in occurence analysis phase (?), getRuntimeRep -------------------------------------+------------------------------------- Reporter: _deepfire | Owner: (none) Type: bug | Status: new Priority: high | Milestone: 8.4.4 Component: Compiler | Version: 8.4.3 Keywords: | Operating System: Linux Architecture: | Type of failure: Compile-time Unknown/Multiple | crash or panic Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Compiling this: {{{#!hs {-# LANGUAGE DataKinds, GADTs, KindSignatures #-} module Holo () where data ADT (p :: Integer) where ADT :: { a :: a , b :: Integer } -> ADT p foo = undefined {b=undefined} }}} ..yields: {{{ ghc: panic! (the 'impossible' happened) (GHC version 8.4.3 for x86_64-unknown-linux): getRuntimeRep p_a29z :: Integer Call stack: CallStack (from HasCallStack): callStackDoc, called at compiler/utils/Outputable.hs:1150:37 in ghc:Outputable pprPanic, called at compiler/types/Type.hs:1967:18 in ghc:Type Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} -v4 suggests this happend during the occurence analysis phase (log attached). -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15499> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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